Loaches Online Forum

Hi
One of my fish died (congo tetra) yesterday but I didn't think much of it as he was very old and not looking great for a while however this morning I found two more fish dead (splash tetra) which prompted me to test the water. The ammonia is 0.25 ppm (I'm guessing this is what cause the fish death) but my other parameters are fine - nitrites 0 and nitrate 10 ppm. I do weekly water changes and clean the external filter every 6-8 weeks (washed in old tank water).
I was hoping that people on her would be able to tell me if the resultant ammonia but fine other parameters was due to the filter not working, is the ammonia not being converted? My tank isn't overstocked by any means.
Thanks for any help that can be given.

More likely that the ammonia spike was caused by the dead fish.

In your situation I would start looking at other possible factors, such as water quality issues, parasites, illness, and bacterial infection.

The first fish could well have died of old age, then was in the tank longer than you thought, and spiked the ammonia enough to kill the others and for the test to show.

I would do a water change, and add a bit more of your dechlorinator, if it locks up ammonia. Read the label- the better ones will even tell you how much to use to lock up how much ammonia.

Thank for your advise. I've done a water change but have also ordered a new external filter as I've been unsure about the one I have now for awhile.
I don't know how often its meant to turn water over but I'm pretty sure that it's not even doing a tank-full (260L) an hour. The current coming out of the intake pipe doesn't seem very strong. It's an aqua one aquis 1250 (came with the tank, I've had it for 4 years) but I've ordered an ehiem pro 3.
When I change filters should I just put the old filter media into the new one? and if it's more efficient how often should I clean the filter? (lots of conflicting messages online)
Thanks again

Great idea for a new filter! Not even a tank per hour is WAY too slow a flow for even fish from relatively still water. I generally aim for about 10 x the tank volume per hour in a combination of filter and power head. I like the Koralia style of power head. If that type is available to you, that would be a good addition to the tank. There are threads here about how to make them 'Loach Safe'.

Yes, save the established media and put it in the new filter, if it fits. Even if you have to chop up the sponges into smaller pieces.
Another way to keep the bacteria is to put the old media in a mesh bag and hang it in the tank. If you set up several bags and remove one per week for 5-6 weeks that will ease the transition, giving the new filter plenty of time to grow new bacteria while the old bacteria is still helping out.

Thanks for the help. The new filter arrived a few days ago and I put the old media into the filter. The ammonia rose for a day but is now steadily reducing so I'm quite happy, almost at 0. (No other fish have died).
How often should I clean the filter (obviously not for a while whilst the bacteria is still establishing itself but afterwards), by clean I mean give it a rinse in old tank water.

Do these powerheads aid in keeping stable parameters? and are they okay to use with a sand substrate?
Thanks

Filter should be cleaned when the water flow starts slowing by just a little bit.
Easiest to do when you are also doing a water change, so if you see the filter slowing on average about every 2 weeks or so, then every other water change (given that most people do weekly water changes.) On the other (non-filter clean day) you can do a little more cleaning in the tank. On the filter cleaning day don't do quite so much in the tank.

Power heads can be used in almost any set up.
The way I arrange them is that the filter is set up first. Then I watch the water flow. Wherever the dirt tends to accumulate is the spot that needs a little more water movement, so I arrange the power head to help out there.
Be careful in a sand substrate. Filters and power heads can blow the sand around, and if the sand gets into the impeller area it can chew up the impeller or the space where it sits, scarring it so it no longer works well. If you hear the impeller making a sort of rattling sound that does not go away when you clean it then the impeller or the sides of the space where it spins may be damaged.

Another way to keep the bacteria is to put the old media in a mesh bag and hang it in the tank. If you set up several bags and remove one per week for 5-6 weeks that will ease the transition, giving the new filter plenty of time to grow new bacteria while the old bacteria is still helping out.

Zeta, if you read my post above in this very thread that is what I already said.